This invention relates to vinyl phosphonate esters which are useful as flame retardants.
Recently, there has been a great deal of interest in providing effective flame retardants for normally flammable substrates. For example, much interest is being shown in compounds which may be added to polyurethane foam to act as flame retardants without destroying the desirable physical characteristics of the foam. In addition, the flame retarding of flammable substrates, such as textiles and thermoplastics, as well as polyurethane foam, for example, has become even more important as a result of recent governmental standards requiring that certain of these substrates be flame retarded.
In the past, however, the flame retarding of flammable substrates has presented some problems which have not been readily overcome. For example, one problem that arises results from the generally high processing temperatures (greater than 270.degree.C.) required during the mixing and extruding of substrates such as thermoplastic fibers, like poly-(ethylene terephthalate) commonly referred to as Dacron. These high processing temperatures can cause the volatilization or thermal degradation of the therein incorporated flame retardant.
Moreover, aside from severe processing conditions, flammable substrates such as polyurethane foam, are generally subjected to ambient conditions which alone are sufficient to cause the volatilization or thermal degradation of a therein incorporated flame retardant. In addition to the loss of flame retardant activity, this degradation of the flame retardant material within the foam substrate may also result in the loss of many of the desired physical characteristics of the foam.
Regarding the flame retardant compounds themselves, while it is generally recognized that compounds which contain, for example, bromine have improved flame retardant capabilities, many of these compounds are unacceptable because of their volatility and thermal instability.
On the other hand, prior art flame retardant compounds have been developed which, while possessing the requisite thermal stability, do not possess sufficient flame retardant activity to allow for efficient use.
Accordingly, there is a need for flame retarding compounds, which while characterized by sufficient thermal stability, also possess efficient flame retardant capability.